Two Stage Methods for Processing Adhesives and Related Compositions

ABSTRACT

Methods for forming melt processable, actinic radiation polymerizable and crosslinkable adhesives are described. In certain versions, the adhesives or pre-adhesive compositions include two initiators and are polymerized and/or crosslinked by exposure to actinic radiation such as UV light or electron beam radiation. Also described are pre-adhesive compositions including polymerizable monomers, articles including the adhesives, and various methods and systems related to the adhesives and their application. In addition, various apparatuses are described for polymerizing or crosslinking the compositions.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims the benefit of U.S. Provisional PatentApplication No. 62/297,170 filed Feb. 19, 2016, which is incorporatedherein by reference in its entirety.

FIELD

The present subject matter relates to methods for preparing adhesives,and particularly melt processable adhesives that are polymerized andcrosslinked by exposure to actinic radiation. In many embodiments, theadhesives are produced from controlled architecture polymers. Thepresent subject matter also relates to adhesive and pre-adhesivecompositions, articles utilizing the adhesives, and systems forprocessing the adhesives.

BACKGROUND

UV curable polymeric systems such as various adhesives and coatings areknown in the art. Typically, exposure to UV light for a sufficientduration and intensity results in crosslinking of the polymer and incertain systems polymerization of monomers or other species. Curingoften results in toughening or hardening of the system.

Although a wide range of equipment and practices are known for curingpolymeric systems, most if not all are limited in flexibility and/or canonly be used in association with specific polymeric systems havingparticular curing requirements. Accordingly, a need exists for newstrategies for curing adhesive systems and new adhesive compositionsthat can be prepared, stored if desired, and selectively applied orfurther processed.

SUMMARY

The difficulties and drawbacks associated with previous approaches areaddressed in the present subject matter as follows.

In one aspect, the present subject matter provides a method of forming amelt processable adhesive. The method comprises providing a compositionthat includes at least one monomer having one or more ethylenicallyunsaturated bonds, a first actinic radiation initiator, and a secondactinic radiation initiator, wherein the second initiator issubstantially non-photoactive at activation wavelength(s) of the firstinitiator. The method also comprises at least partially polymerizing thecomposition by exposing the composition to radiation having wavelengthscorresponding to the activation wavelength(s) of the first initiator.The method additionally comprises at least partially crosslinking thecomposition to thereby form the adhesive by exposing the composition toradiation having wavelengths corresponding to the activationwavelength(s) of the second initiator. In this method, the compositionis free of solvents.

In another aspect, the present subject matter provides a method offorming an adhesive by two stages involving exposure to actinicradiation. The method comprises providing a composition including atleast one monomer, a first actinic radiation initiator, and a secondactinic radiation initiator, wherein the second initiator issubstantially non-photoactive at activation wavelength(s) of the firstinitiator. The method also comprises at least partially polymerizing thecomposition by exposing the composition to radiation having wavelengthscorresponding to the activation wavelength(s) of the first initiator.The method additionally comprises at least partially crosslinking thecomposition to thereby form the adhesive by exposing the composition toradiation having wavelengths corresponding to the activationwavelength(s) of the second initiator. At least one of the first and thesecond initiators is a polymer having a photoinitiator moiety along thepolymer backbone.

In yet another aspect, the present subject matter provides a compositioncomprising at least one monomer having one or more ethylenicallyunsaturated bonds in which the composition can be readily processed toform an adhesive. The composition also comprises a first actinicradiation initiator for at least partially polymerizing the at least onemonomer to form a pre-adhesive, the first initiator being activated at afirst activation wavelength(s). The composition additionally comprises asecond actinic radiation initiator for at least partially crosslinkingthe pre-adhesive, the second initiator being activated at a secondactivation wavelength(s) and the second initiator being substantiallynon-photoactive at the first activation wavelength(s).

In still another aspect, the present subject matter provides an acrylatemelt processable pre-adhesive composition comprising at least oneacrylate polymer. The composition also comprises an actinic radiationinitiator for at least partially crosslinking the polymer, the initiatorbeing a photoinitiator moiety along the polymer backbone. Thepre-adhesive composition prior to activation of the initiator exhibits aviscosity within a range of from 1,000 cps to 80,000 cps at atemperature within a range of from 110° C. to 180° C.

In yet another aspect, the present subject matter provides an apparatusfor polymerizing and/or crosslinking an adhesive or pre-adhesivecomposition. The apparatus comprises a reaction vessel defining aninterior chamber and including at least one collar providing access tothe interior chamber. The apparatus also comprises at least one probeassembly supported by the collar. The probe assembly includes (i) anemitter for emitting light that polymerizes and/or crosslinks thecomposition, (ii) a light tube extending from the emitter and at leastpartially disposed within the interior chamber of the reaction vessel,(iii) adjustable positioning provisions for governing position of thelight tube within the interior chamber of the reaction vessel, and (iv)a cover disposed at a distal end of the light tube, wherein the cover istransparent or substantially transparent to passage of light emittedfrom the emitter.

In still another aspect, the present subject matter provides anapparatus for polymerizing and/or crosslinking an adhesive orpre-adhesive composition. The apparatus comprises a reaction vesseldefining an interior chamber and at least one sight glass incorporatedin a wall of the vessel and providing visual access to the interiorchamber. The apparatus also comprises at least one probe assemblyadjacent the sight glass. The probe assembly includes an emitter foremitting light that polymerizes and/or crosslinks the composition. Theprobe assembly is positioned such that light emitted from the emitter isdirected to the sight glass and passes into the interior chamber of thereaction vessel. The sight glass is transparent or substantiallytransparent to passage of light emitted from the emitter.

In another aspect, the present subject matter provides an apparatus forpolymerizing and/or crosslinking an adhesive or pre-adhesivecomposition. The apparatus comprises a reaction vessel defining aninterior chamber, and including mixing provisions having at least oneblade. The apparatus also comprises at least one baffle disposed withinthe interior chamber of the reaction vessel. The baffle includes atleast one emitter for emitting light that polymerizes and/or crosslinksthe composition.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration depicting a conventional polymerincluding various reactive functional groups and upon exposure to UVradiation, formation of a conventional randomly crosslinked network.

FIG. 2 is a schematic illustration depicting controlled architecturepolymers (CAPs) and upon exposure to UV radiation, formation of enhancedterminally linked networks in accordance with the present subjectmatter.

FIG. 3 is a schematic illustration of a conventional randomlycrosslinked network and, upon incorporation in an adhesive, typicaladhesive properties associated with such network.

FIG. 4 is a schematic illustration of an enhanced terminally linkednetwork and, upon incorporation in an adhesive, typical adhesiveproperties associated with such network in the adhesive in accordancewith the present subject matter.

FIG. 5 is a process schematic diagram showing a representative processand system for producing an adhesive in accordance with the presentsubject matter.

FIG. 6 is a schematic flow chart of a method for forming an adhesive inaccordance with the present subject matter.

FIG. 7 is a schematic illustration of a tape article including anadhesive in accordance with the present subject matter.

FIG. 8 is a schematic cross sectional view of another tape article inaccordance with the present subject matter.

FIG. 9 is a schematic cross sectional view of another tape article inaccordance with the present subject matter.

FIG. 10 is a schematic cross sectional view of another tape article inaccordance with the present subject matter.

FIG. 11 is a schematic cross sectional view of another tape article inaccordance with the present subject matter.

FIG. 12 is a schematic cross sectional view of a sealing or closureassembly including a region of an adhesive in accordance with thepresent subject matter.

FIG. 13 is a schematic illustration of an embodiment of an apparatus forpolymerizing and/or crosslinking adhesives in accordance with thepresent subject matter.

FIG. 14 is a schematic illustration of another version of an apparatusfor polymerizing and/or crosslinking adhesives in accordance with thepresent subject matter.

FIG. 15 is a schematic illustration of another version of an apparatusfor polymerizing and/or crosslinking adhesives in accordance with thepresent subject matter.

FIG. 16 is a schematic illustration of another version of an apparatusfor polymerizing and/or crosslinking adhesives in accordance with thepresent subject matter.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The present subject matter relates to methods for preparing adhesivesand particularly actinic radiation polymerizable and crosslinkable meltprocessable adhesives. In many embodiments of the present subjectmatter, the methods are directed to forming adhesives produced fromcontrolled architecture polymers (referred to as “CAPs” herein). Thepresent subject matter also relates to adhesives and pre-adhesivesformed by the methods noted herein. The present subject matter alsorelates to articles containing the adhesives prepared by the methodsdescribed herein. In addition, the present subject matter relates toequipment and systems for preparing and/or processing the adhesives andpre-adhesives.

Before turning attention to the details of the present subject matterand the numerous embodiments thereof, it is instructive to considerseveral terms and their definitions as used herein. The terms“polymerize” or “polymerizing” refer to a process of reacting monomerstogether in a chemical reaction to form polymer. And the terms“crosslink” or “crosslinking” refer to a process of forming bonds thatlink one polymer chain to another polymer chain. The bonds may becovalent bonds or ionic bonds. The term “crosslink” can refer to thebond itself. The terms “cure” and “curing” refer to the terms“crosslink” or “crosslinking” and are used interchangeably.

In many embodiments of the present subject matter methods, uponpolymerizing and crosslinking of certain compositions, and particularlythose that include CAPs, the resulting adhesives exhibit enhancedadhesive properties such as relatively high peel strength and shearstrength. These enhanced adhesive properties are believed to at leastpartially result from (i) a majority of crosslinking involvingfunctional group(s) of the polymers being located at or near terminalends of the polymer chains, and (ii) an absence or only a minority ofcrosslinking involving functional group(s) located within interiorregions of the polymer chains. The crosslinked network that results fromthe methods as described herein is referred to herein as an “enhancedterminally linked network” or ETLN. As described in greater detailherein, formation of an ETLN allows for lower adhesive coatweights,lower viscosities, and better adhesive performance, among various otheradvantages and benefits. These and other aspects of the methods, the CAPbased adhesives and ETLNs, and related articles are described in greaterdetail herein.

Although in many embodiments, the present subject matter methods utilizeadhesives including CAPs, it will be appreciated that the presentsubject matter also includes methods of polymerizing and crosslinkingnon-CAP based adhesives. These and other aspects of the methods, thenon-CAP based adhesives polymerized and crosslinked by such methods, andrelated articles are described in greater detail herein.

The present subject matter also provides pre-adhesive compositions thatinclude one or more monomers which upon polymerization form an adhesivebase polymer. The pre-adhesive composition also includes at least twoactinic radiation initiators. In many embodiments at least one of theseinitiators, and in particular embodiments both the first and the secondinitiators, polymerize with the monomers to form the adhesive. These andother aspects are described herein.

The present subject matter also provides a block copolymer compositioncomprising at least one of an (AB) diblock copolymer, (ABA) triblockcopolymer, an -(AB)_(n)- multiblock copolymer, and combinations thereof.The present subject matter also provides a pressure sensitive adhesivederived from a block copolymer composition comprising at least one of an(AB) diblock copolymer, (ABA) triblock copolymer, an -(AB)_(n)-multiblock copolymer, and combinations thereof. The present subjectmatter further provides a method of preparing a block copolymer (and/ora method of preparing a pressure sensitive adhesive derived from a blockcopolymer composition) comprising at least one of an (AB) diblockcopolymer, (ABA) triblock copolymer, an -(AB)_(n)- multiblock copolymer,and combinations thereof. The present subject matter also provides useof a block copolymer (and/or a pressure sensitive adhesive derived froma block copolymer) composition comprising at least one of an (AB)diblock copolymer, (ABA) triblock copolymer, an -(AB)_(n)- multiblockcopolymer, and combinations thereof. The block copolymer of the presentsubject matter may be an acrylic block copolymer. In other embodiments,the block copolymer of the present subject matter is preferably anacrylic block copolymer.

Adhesives

The actinic radiation polymerizable and crosslinkable adhesives of thepresent subject matter comprise a melt adhesive or pre-adhesivecomposition, a first actinic radiation initiator that in manyapplications serves to polymerize the adhesive and a second actinicradiation initiator that is useful for crosslinking the adhesive. Inmany embodiments, the second initiator is substantially non-photoactiveat activation wavelengths of the first initiator.

In many embodiments, the actinic radiation polymerizable andcrosslinkable melt adhesive includes controlled architecture polymers orCAPs. In many embodiments of the present subject matter, the CAPs arethose described in one or more co-pending applications owned by theApplicant which include US 2011/0118372; US 2013/0059971; and US2014/0329958. Details of particular embodiment polymers are providedherein. However, it will be understood that the present subject matterincludes the use of any of the polymers described in these applications.

In certain embodiments, upon activation of the first initiator to form apre-adhesive, the pre-adhesive exhibits a viscosity within a range offrom 1,000 cps to 80,000 cps at a temperature within a range of from110° C. to 180° C. In particular embodiments, the pre-adhesive exhibitsa viscosity within a range of from 30,000 cps to 40,000 cps at atemperature within a range of from 120° C. to 140° C. In otherembodiments, the pre-adhesive exhibits a viscosity within a range offrom 40,000 cps to 50,000 cps at a temperature within a range of from120° C. to 140° C. And, in still other embodiments, the pre-adhesiveexhibits a viscosity within a range of from 1,000 cps to 15,000 cps at atemperature within a range of from 110° C. to 130° C.

It will be understood that in no manner is the present subject matterlimited to adhesives or pre-adhesives exhibiting these particularviscosities. It is contemplated that the present subject matter may alsoinclude adhesives or pre-adhesives exhibiting these viscosities attemperatures less than 110° C., and/or at temperatures greater than 180°C. Moreover, it is contemplated that the present subject matter may alsoprovide adhesives or pre-adhesives that exhibit viscosities less than1,000 cps and/or greater than 80,000 cps at a wide array oftemperatures.

The present subject matter adhesives and/or pre-adhesive compositionscomprise two or more actinic radiation initiators and in particularembodiments two or more UV activated initiators. Although not wishing tobe bound by any particular theory, it is believed that in manyembodiments of the present subject matter, one or both initiator(s),when irradiated with actinic radiation and particularly UV light, isexcited to a higher energy state and abstracts a hydrogen atom from afunctional group on the polymer, thereby generating a free radical thatis available for further reaction, such as for example free radicaladdition crosslinking with another polymer chain or functional group onthe polymer. However, it will be understood that the present subjectmatter includes the use of nearly any type of initiator and is notlimited to those that abstract hydrogen atoms. For example, a variety ofinitiators are known that decompose or cleave into free radicals uponexposure to light, and more particularly UV radiation.

A variety of initiators are known and can potentially be incorporated inthe present subject matter adhesives, including benzophenone,acetophenone, acyl phosphine, thioxanthone, derivatives of thesecompounds, and similar compounds. Each compound functions as aphotoinitiator by absorbing energy within the UV region of theelectromagnetic spectrum.

Several types of photoinitiators that absorb in the near UV region ofthe spectrum are known, including acylphosphine oxide-typephotoinitiators, redshifted benzophenone-type photoinitiators, andthioxanthone-type photoinitiators. Many of these may be suitable for usewith the present subject matter compositions.

Commercially available acylphosphine oxide-type photoinitiators include“Lucirin TPO” (2,4,6-trimethylbenzoyldiphenylphosphine oxide) and“Lucirin TPO-L” (liquid), sold by BASF, and “BAPO” (bis2,6-dimethoxybenzoyll-2,4-trimethylpentylphosphine oxide), sold by Ciba.

The so-called “redshifted benzophenone-type photoinitiators” arebenzophenone derivatives in which one or more hydrogen atoms is replacedby a functional group or groups which cause a redshift (towards longerwavelengths) in the UV absorption spectrum of the molecule, as comparedto the UV absorption spectrum of benzophenone. An example is “QUANTACUREBMS” (4-benzoyl-4′-methyldiphenylsulfide).

Commercially available thioxanthone-type photoinitiators include“Quantacure ITX,” which is believed to be a mixture of 2-isopropyl- and4-isopropylthioxanthone isomers.

Other suitable photoinitiators can be identified by those skilled in theart and utilized in the present subject matter. Moreover, if theadhesive is compounded without a pigment, photoinitiators that absorb atshorter UV wavelengths can be employed, including less expensive,simpler photoinitiators such as unsubstituted acetophenone, benzil,benzophenone, quinone, and thioxanthone.

Combinations of any of the noted photoinitiators can potentially be usedfor the first initiator, the second initiator, and/or both initiators,

In certain embodiments of the present subject matter, particularinitiators are used which are in the form of polymerizable monomers.During formation of the polymer(s) of the adhesives, the first and/orsecond initiators are incorporated in the adhesive polymers and can besubsequently activated by UV irradiation. Thus, at least one of thefirst and second initiators is polymerizable with the monomers that formthe adhesive and/or its polymers. In these embodiments, the firstinitiator is a polymerizable photoinitiator and initiates polymerizationof the monomers that form the adhesive. Polymerization of the monomersmay be initiated either directly or indirectly via sensitization,synergists, or co-initiator mechanisms. Nonlimiting examples ofpolymerizable photoinitiators include acyl phosphines, thioxanthonederivatives, camphorquinone and/or related derivatives, and combinationsthereof. Examples of acyl phosphines include TPO, TPO-L, and BAPO.However, it will be understood that the present subject matter includesother agents that absorb UV radiation and which may be suitable for useas the first initiator. For example, it is contemplated that the UVabsorbing material can be in the form of a distinct agent that is addedto the system, bound to a polymer, or formed in-situ by an associationof materials or agents in the system. This latter strategy is referredto herein as a “photoinitiator free” technique and can be based uponcomplexes such as a charge transfer complex or a donor-acceptor complex.

In these embodiments, the second initiator is in the form of apolymerizable monomer having a photoinitiator moiety attached or coupledthereto. Generally, the polymerizable monomer can be any monomersuitable for forming the polymeric matrix of the adhesive system.Nonlimiting examples of such monomers include acrylate and methacrylatemonomers. Additional examples of potentially suitable monomers aredescribed herein.

The photoinitiator moiety of this version of the second initiator mustnot be appreciably photoactive at wavelengths at which the firstinitiator activates. Thus, the photoinitiator moiety is generallyinactive at the activation wavelengths of the first initiator.

Generally, the photoinitiator moiety of the polymerizable monomerversion of the second initiator is a hydrogen abstractor type initiator.For example, the moiety may include a derivative of benzophenone.However, the present subject matter includes cleavage typephotoinitiators. Furthermore, the present subject matter includesactivation via sensitizers, co-initiators, and/or synergists. Aspreviously described for the first polymerizable initiator, the secondinitiator in the form of a polymerizable monomer having a photoinitiatormoiety can be in the form of a distinct agent that is added to thesystem, bound to a polymer, or formed in-situ by an association ofmaterials or agents in the system in a photoinitiator-free techniquesuch as based upon complexes such as a charge transfer complex or adonor-acceptor complex.

As noted, in many embodiments the adhesives utilize a first initiatorand a second initiator which are activated at different wavelengths.This enables activation of the first initiator without activating thesecond initiator. The initiators are both activated by actinic radiationand in many embodiments by UV radiation, i.e., electromagnetic radiationhaving a wavelength in a range of from about 100 nm to about 500 nm. Incertain embodiments, the first initiator is activated at wavelengthswithin a range of from 200 nm to 500 nm, particularly from 300 nm to 500nm, and more particularly from 350 nm to 500 nm. And, the secondinitiator is activated at wavelengths within a range of from 100 nm to400 nm, particularly from 200 nm to 400 nm, and more particularly from200 nm to 375 nm. Generally, the wavelength(s) at which the firstinitiator is activated is (are) different from those at which activationoccurs for the second initiator.

Thus, in many versions of the present subject matter, one or both of thefirst and second initiators is/are in the form of a polymer having aphotoinitiator moiety along the polymer backbone. And, in certainembodiments, one or both of the first and second initiators is/are inthe form of polymerizable monomers and/or oligomers having aphotoinitiator moiety.

The first and/or second initiators can also be activated by exposure toelectron beam radiation. It is also contemplated that one initiator canbe activated by exposure to UV radiation and another initiator can beactivated by exposure to electron beam radiation.

The total amount of initiators added to the polymer in preparing theadhesive depends on several factors, including the amount of pigmentand/or other agents added, the coat weight (thickness) of the adhesiveon the substrate, the web speed during curing, and the type and cost ofthe initiators used. In many embodiments, the initiator is the mostexpensive ingredient in the adhesive. Therefore, ordinarily it isdesirable to minimize the amount of initiator added to the polymer, solong as enough initiator is included to achieve the desired endproperties of the resulting composition.

In certain embodiments of the present subject matter, a pigment or othercoloring agent(s) is added to the composition, typically prior tocrosslinking, in order to render the adhesive opaque, and/or to impartcolor to the adhesive. Opaque pigments such as for example titaniumdioxide typically are added by the coating industry precisely because oftheir high hiding power. However, their presence generally interfereswith UV initiated crosslinking of the adhesive polymer. In the presentsubject matter, however, initiators that absorb in the near UV region ofthe spectrum can be employed with pigmented (as well as non-pigmented)formulations, thereby avoiding interference with UV initiatedcrosslinking of the adhesive.

The amount of pigment added to the compounded polymer in a givenformulation, like the amount of initiator, depends on a number offactors, including the desired degree of opacity, desired degree ofcure, whether other fillers are present, the type and amount ofphotoinitiator present, and cost considerations.

For the present subject matter, where pigmented adhesive compositionsare utilized, UV initiated crosslinking can be facilitated by decreasingthe amount of titanium dioxide present (or other pigment) and/orincreasing the amount of initiator. As a practical matter, though,pigment loadings above about 15 parts pigment per hundred parts polymer(or, if the copolymer is tackified, about 15 parts pigment per 100 partspolymer plus tackifier) are less preferred than lower pigment loadings.UV initiated crosslinked, pressure sensitive adhesive compositionshaving high cohesive strength can be prepared in accordance with thepresent subject matter with higher pigment loadings, but require higher(and more expensive) initiator concentrations and/or longer crosslinkingtimes.

In some embodiments, the adhesive composition is formulated with acolored (non-white) pigment.

Generally, yellow and red pigments do not substantially interfere withphotoinitiators that absorb in the UV region. Hence, adhesivescompounded with such pigments can be UV crosslinked to a high cohesivestrength by using UV-activatable, photoinitiators. Blue pigments tend toabsorb strongly in at least part of the near UV region. By minimizingthe amount of blue pigment that is added, however, UV crosslinkedadhesives can be prepared in the manner described herein.

In addition to the pigment and initiator(s), in some embodiments, thepolymer is further compounded with a tackifier. In certain embodimentssuch as if the adhesive is a pressure sensitive adhesive, tackifier maybe added to improve the tack of the pressure sensitive adhesive.

A variety of tackifiers, many of which are well known in the industry,can potentially be used in the practice of the present subject matter.Representative, nonlimiting examples of such tackifiers includehydrocarbon resins and rosin resins. Such tackifiers include, but arenot limited to, rosins and rosin derivatives including rosinousmaterials that occur naturally in the oleoresin of pine trees, as wellas derivatives thereof including rosin esters, modified rosins such asfractionated, hydrogenated, dehydrogenated, and polymerized rosins,modified rosin esters and the like. Generally, up to about 45 partstackifier per hundred parts polymer are added. However, it will beappreciated that the present subject matter includes the use of lesseramounts and/or greater amounts of tackifiers.

A wide range of tackifiers are commercially available including, but notlimited to, Foral® 85 (glycerol ester of a highly stabilized rosin),Foral® 105 (pentaerythritol ester of a hydrogenated rosin), Stabiliteester 10, and Pentalyn® H, manufactured and sold by Hercules, Inc., PEEstergum and the like, manufactured by Arizona Chemical Co., andSylvatac® 40N, Sylvatac® RX, Sylvatac® 95 and the like, manufactured bySylvachem Corporation.

There may also be employed as tackifiers terpene resins which arehydrocarbons of the formula C10H16, occurring in most essential oils andoleoresins of plants, and phenol modified terpene resins like alphapinene, beta pinene, dipentene, limonene, myrecene, bomylene, camphene,and the like. Various aliphatic hydrocarbon resins like Escorez™ 1304,manufactured by Exxon Chemical Co., and aromatic hydrocarbon resinsbased on C9's, C5's, dicyclopentadiene, coumarone, indene, styrene,substituted styrenes and styrene derivatives and the like can also beused.

Hydrogenated and partially hydrogenated resins such as Regalrez™ 1018,Regalrez™ 1033, Regalrez™ 1078, Regalrez™ 1094, Regalrez™ 1126,Regalrez™ 3102, Regalrez™ 6108, etc., produced by Hercules Corporation,can be used as tackifiers in the present subject matter as well. Variousterpene phenolic resins of the type SP 560, manufactured and sold bySchenectady Chemical Inc., Nirez 1100, manufactured and sold by ReicholdChemical Inc., and Piccolyte® S-100, manufactured and sold by HerculesCorporation, are particularly useful tackifiers for the present subjectmatter. Further, various mixed aliphatic and aromatic resins, such asHercotex AD 1100, manufactured and sold by Hercules Corporation, canalso be used as tackifiers.

Additionally, the melt processable, actinic radiation polymerizable andcrosslinkable adhesive compositions may comprise one or more inhibitors.A viable free radical scavenger may be present to prevent prematuregelation, either in storage or preparation for coating, especially inthe case of hot melt adhesive compositions. Inhibitors comprisingphenolic compounds are one class of such materials that may be used inthe present subject matter, including, for example, 4-methoxyphenol(MEHQ, methyl ether of hydroquinone), hydroquinone,2-methylhydroquinone, 2-t-butylhydroquinone, t-butyl catechol, butylatedhydroxy toluene, and butylated hydroxy anisole and the like andcombinations thereof. Other inhibitors that may be used includephenothiazine and anaerobic inhibitors, such as the NPAL type inhibitors(tris-(N-nitroso-N-phenylhydroxylamine) aluminum salt) from AlbemarleCorporation, Baton Rouge, La. Combinations of inhibitors may be used.

The adhesives of the present subject matter may further comprise one ormore conventional adjuvants such as fillers, plasticizers, diluents, andthe like. Combinations of one or more of these components can be usedincluding combinations with pigment(s) and/or tackifier(s). If desired,diluents such as plasticizers may be added in the place of a portion ofthe tackifier in order to alter the properties of tackiness and cohesivestrength.

Generally, the melt processable, actinic radiation polymerizable andcrosslinkable adhesives include at least 95% solids, in many embodimentsat least 98% solids, in particular embodiments at least 99% solids, andin certain versions at least 99.5% solids.

As noted, in many embodiments of the present subject matter theadhesives are in the form of pressure sensitive adhesives. A descriptionof pressure sensitive adhesives and their characteristics may be foundin Encyclopedia of Polymer Science and Engineering, Vol. 13.Wiley-Interscience Publishers (New York, 1988). Additional descriptionof pressure sensitive adhesives and their characteristics may be foundin Encyclopedia of Polymer Science and Technology, Vol. 1, IntersciencePublishers (New York, 1964).

Controlled Architecture Polymers (CAPs)

In particular embodiments, the melt processable, actinic radiationpolymerizable and crosslinkable adhesives of the present subject matterare produced from controlled architecture polymers. In many embodimentsthe polymers are acrylic polymers.

In many embodiments of the present subject matter, the melt processable,actinic radiation polymerizable and crosslinkable adhesives that includecontrolled architecture polymers have one or more reactive functionalgroups incorporated in select blocks or regions of the polymer atdesignated concentrations within those regions. As noted, in manyembodiments the polymers are acrylic polymers. The reactive functionalgroups can be incorporated in the polymers by one or more polymerizablemonomers as described herein. Thus, a polymerizable monomer and/orcomonomer as described herein may constitute one or more reactivefunctional groups. The present subject matter additionally providesadhesives utilizing the controlled architecture polymers.

Generally, the CAPs comprise at least two blocks or regions differentfrom one another, located anywhere along the polymer backbone or chain,or elsewhere within the polymer. Thus, a CAP as described herein maycontain one or more A blocks, one or more B blocks, and one or more Cblocks anywhere within the polymer. The preferred polymers may compriseother types of blocks or regions such as D blocks, E blocks . . . etc.In a preferred aspect, particular amounts of reactive functional groupsare provided in association with at least two of the blocks, referred asblocks A and B for purposes of convenience. And, in a more preferredaspect, the amounts of reactive functional groups are controlled in theblocks A and B such that the total amount of a reactive functional groupis distributed between two blocks, for example blocks A and B, within acertain range of weight ratios. Generally, this ratio is referred toherein as an “apportionment ratio” and is defined as the ratio of theweight percent of a reactive functional group associated with block A tothe weight percent of the reactive functional group associated withblock B. Generally, a useful range of ratios, i.e. apportionment ratios,for the controlled architecture polymers described herein is from about1.1:1 to about 10,000:1. In many embodiments, the apportionment ratiosof the ordered polymers are from 1.1:1 to 1,000:1, or from 1.1:1 to100:1. In other embodiments, the apportionment ratios of the orderedpolymers are from 6:1 to 10,000:1, or from 6:1 to 1,000:1, or from 6:1to 100:1, or from 6:1 to 80:1. However, it will be appreciated that thepresent subject matter includes polymers with one or more reactivefunctional groups distributed between polymeric blocks at apportionmentratios less than or greater than these ranges. For example, the presentsubject matter includes polymers as described herein however havingapportionment ratios in excess of 10,000:1, such as for example about50,000:1, about 75,000:1, and about 100,000:1.

The CAPs are preferably formed from (i) monomers of acrylates and/ormethacrylates and (ii) polymerizable acrylate comonomers having one ormore reactive functional groups. The term “monomer” or “comonomer” asused herein refers to a molecule, starting unit, or chemical speciesthat can bond together to form a polymer. The term also includes arepeating unit within the polymer. As noted, these monomers orcomonomers are generally referred to herein as blocks or regions such as“A”, “B”, and/or “C”. The acrylate monomers include C1 to about C20alkyl, aryl or cyclic acrylates such as methyl acrylate, ethyl acrylate,phenyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, isobornylacrylate and functional derivatives of these acrylates such as 2-hydroxyethyl acrylate, 2-chloro ethyl acrylate, and the like. These monomers orcomonomers typically contain from about 3 to about 20 carbon atoms, andin one embodiment about 3 to about 8 carbon atoms. The methacrylatemonomers include C1 to about C20 alkyl, aryl or cyclic methacrylatessuch as methyl methacrylate, ethyl methacrylate, butyl methacrylate,2-ethylhexyl methacrylate, phenyl methacrylate, isobornyl methacrylate,and functional derivatives of these methacrylates such as 2-hydroxyethylmethacrylate, 2-chloroethyl methacrylate, and the like. These monomersor comonomers typically contain from about 4 to about 20 carbon atoms,and in one embodiment about 4 to about 8 carbon atoms. Combinations ofacrylates and methacrylates can also be used.

Although in many embodiments the CAPs preferably comprise (i) monomersof acrylates and/or methacrylates, and (ii) polymerizable acrylatecomonomers, i.e. blocks A and B, the present subject matter includes theuse of additional and/or different monomers as blocks in the polymer.Nearly any free radically polymerizable monomer or combination ofmonomers could be used as blocks A, B, C, D, E, etc. in the controlledarchitecture polymers described herein. Accordingly, it will beunderstood that in no way is the present subject matter limited to theCAPs including acrylate and/or methacrylate blocks.

The polymerizable monomers and comonomers can include as reactivefunctional groups acrylonitrile groups, acrylamide groups,methacrylamide groups, vinyl ester groups, vinyl ether groups, vinylamide groups, vinyl ketone groups, styrene groups, halogen-containinggroups, ionic groups, acid-containing groups, base-containing groups,olefin groups, silane groups, epoxy groups, hydroxyl groups, anhydridegroups, and mixtures of two or more groups thereof. It is alsocontemplated to include silyl groups, carboxyl groups, carbonyl groups,carbonate ester groups, isocyanato groups, amino groups, amide groups,imide groups, mercapto groups, and acetoacetyl groups in any combinationand/or in combination with one or more of any of the previously notedgroups.

The acrylonitrile groups can include acrylonitrile and alkyl substitutedacrylonitriles. The alkyl groups typically contain from 1 to about 20carbon atoms, and in one embodiment from 1 to about 10 carbon atoms, andin another embodiment from 1 to about 5 carbon atoms. Examples includemethacrylonitrile and ethacrylonitrile.

The acrylamide groups can include acrylamide and its derivativesincluding the N-substituted alkyl and aryl derivatives thereof. Theseinclude N-methyl acrylamide, N,N-dimethyl acrylamide, t-octylacrylamide, N-aminoethyl acrylate, N-aminoethyl methacrylate, and thelike.

The methacrylamide groups can include methacrylamide and its derivativesincluding the N-substituted alkyl and aryl derivatives thereof.

The vinyl ester groups can include vinyl acetate, vinyl propionate,vinyl butyrate, vinyl valerate, vinyl versitate, vinyl isobutyrate, andthe like.

The vinyl ether groups can include vinyl ethers having 1 to about 8carbon atoms including ethylvinyl ether, butylvinyl ether,2-ethylhexylvinyl ether, and the like.

The vinyl amide groups can include vinyl amides having 1 to about 8carbon atoms including vinyl pyrrolidone, and the like.

The vinyl ketone groups can include vinyl ketones having 1 to about 8carbon atoms including ethylvinyl ketone, butylvinyl ketone, and thelike.

The styrene groups can include styrene, indene, and substituted styrenesrepresented by the formula (I):

wherein each of A, B, C, D, E and F is independently selected fromhydrogen, C1 to about C4 alkyl or alkoxy groups (especially methyl ormethoxy groups,) halogroups (especially chloro), thio, cyano, carboxylicacid or ester, or fluorinated alkyl groups of 1 to about 4 carbon atoms.Examples include methyl styrene (sometimes referred to as vinyltoluene), alpha-methyl styrene, divinylbenzene, chlorostyrene,chloromethyl styrene, and the like.

The halogen-containing groups can include vinyl chloride, vinyl bromide,vinyl fluoride, vinylidene chloride, vinylidene bromide, vinylidenefluoride, halogen substituted propylene monomers, and the like, withvinyl bromide and vinylidene chloride being preferred.

The ionic groups can include sodium vinyl sulfonate, sodium styrenesulfonate, sodium methallyl sulfonate, sodium acrylate, sodiummethacrylate, and the like, with sodium vinyl sulfonate, sodium styrenesulfonate and sodium methallyl sulfonate being preferred.

The acid-containing groups can include unsaturated carboxylic acidscontaining from 3 to about 20 carbon atoms. Preferred groups includeacrylic acid, methacrylic acid, vinyl sulfonic acid, itaconic acid, betacarboxyl ethyl acrylate, mono-2-acroyloxypropyl succinate, and the like.

The base-containing groups can include vinyl pyridine and the like.

The olefin groups can include isoprene, butadiene, C2 to about C8straight chained and branched alpha-olefins such as ethylene, propylene,butylene, isobutylene, diisobutylene, 4-methyl pentene-1, 1-butene,1-hexene, 1-octene, and the like.

The silane groups can include vinyltrimethoxysilane,vinyltriethoxysilane, vinyltripropoxysilane, vinylmethyldimethoxysilane,vinylmethyldiethoxy-silane, vinylmethyldipropoxysilane,γ-methacryloxypropyl-trimethoxysilane,γ-methacryloxypropyltriethoxysilane,γ-methacryloxypropyl-tripropoxysilane, γ-methacryloxydimethoxysilane,γ-methacryloxypropyl-methyldimethoxysilane,γ-methacryloxypropylmethyldiethoxysilane,γ-methacryl-oxypropylmethyldipropoxysilane,γ-methacryloxymethyl-dimethoxysilane,γ-methacryloxymethyltrimethoxysilane,γ-methacryloxymethyl-triethoxy-silane, (methacryloxymethyl)methyldimethoxysilane, (methacryloxymethyl)-methyldiethoxysilane,γ-methacryloxypropyltriacetoxysilane, γ-acryloxypropyltrimethoxy-silane,γ-acryloxypropyltriethoxy-silane, γ-methacryl-oxymethyldiethoxysilane,γ-acryloxypropyltripropoxy-silane,γ-acryloxypropyl-methyldimethoxysilane,γ-acryloxypropylmethyldiethoxysilane,γ-acryloxypropyl-methyldipropoxysilane, and the like.

The epoxy groups can include for example, glycidyl methacrylate andglycidal acrylate.

The hydroxyl groups can include for example hydroxy ethyl acrylate,hydroxyl ethyl methacrylate, hydroxyl isopropyl acrylates, hydroxylisopropyl methacrylate, hydroxyl butyl acrylate, hydroxyl butylmethacrylate and the like.

The anhydride groups can include for example maleic anhydride, itaconicanhydride, citraconic anhydride and the like.

In addition to the monomer having functional group(s), the reactivesegment may include at least one monomer having the formula (II):

where R₃ is H or CH₃ and R₄ is a branched or unbranched, saturated alkylgroup having 4 to 14 carbon atoms. The reactive segment may instead oradditionally include at least one monomer having the formula (III):

where R is H or CH₃ and X represents or contains a functional groupcapable of crosslinking.

Representative preferred reactive functional groups for incorporating inthe polymers described herein include, but are not limited to, acrylicacid, 2-methacryloxyethylphthalic acid (PAMA), and combinations thereof.It will be appreciated that a wide array of other reactive functionalgroups can be used instead of or in conjunction with any of thesereactive functional groups.

The CAPs may exhibit particular distributions of reactive functionalgroups throughout the polymer. The distribution of each type of reactivefunctional group incorporated into a polymer can be expressed in termsof a weight ratio of the weight percent amount of that reactivefunctional group in one block or region, i.e. block A, and the weightpercent amount of that reactive functional group in another block orregion, i.e. block B. As noted, this weight ratio is referred to hereinas the apportionment ratio. For many applications of interest, it ispreferred to incorporate greater amounts of reactive functional groupsin an A block of a polymer as compared to amounts of reactive functionalgroups in a different block, i.e. a B block. Therefore, by strategicallylocating particular blocks having certain weight percentages ofspecified reactive functional groups within a polymer, precise polymericarchitectures can be produced, each with desired loading and placementof functional groups within the polymer. This strategy enables theformation of polymers having particular blocks located at desiredregions within the polymer, and the resulting polymer having particularconcentrations of functional groups within the desired regions. Forexample, it may be desired to produce a polymer having a certaincombination of blocks, e.g. A, B, and C, and for such polymer to exhibita relatively high concentration of functional groups within the endregions or other locations of the polymer as compared to other regionssuch as the interior of the polymer.

The present subject matter is applicable to a wide array of polymersizes and weights. Typically, the present subject matter is applicableto polymers having a molecular weight of from about 10,000 to about300,000, preferably from about 50,000 to about 200,000, and mostpreferably from about 100,000 to about 150,000 g/mol. However, it willbe understood that in no way is the present subject matter limited tothese molecular weights. It will be appreciated that these molecularweights for the noted polymers are average molecular weights and unlessindicated otherwise, are weight average molecular weights.

In certain embodiments, the polymers exhibit relatively narrow ranges ofmolecular weight and thus have relatively low polydispersity values.Typically, the preferred embodiment polymers exhibit polydispersity(Pdi) values of less than 4.0, preferably less than 3.5, more preferablyless than 3.0, more preferably less than 2.5, and most preferably lessthan 2.0. In certain embodiments, the preferred embodiment polymersexhibit polydispersities of less than 1.5, and as low as about 1.4.

As previously noted, it will also be understood that the CAPs mayinclude two or more different types of reactive functional groups. Thus,different reactive functional groups can be incorporated into one ormore end region(s) and/or into one or more interior regions of thepolymer(s) of interest. Therefore, a polymer of the present subjectmatter can include 1, 2, 3, or more different reactive functionalgroups. And, each group can be defined as apportioned along the polymerin a particular ratio as described herein. For example, a CAP caninclude a first reactive functional group apportioned between blocks Aand B at a first apportionment ratio, and a second reactive functionalgroup apportioned between blocks A and B at a second apportionment ratiodifferent from the first apportionment ratio. Moreover, it is alsocontemplated that the second reactive functional group or a thirdreactive functional group could be apportioned between one of blocks Aand B, and another block, block C. Alternatively, the second or thirdreactive functional group could be apportioned between a set of blocksdifferent from blocks A and B, such as blocks C and D.

Representative and non-limiting examples of ranges of glass transitiontemperatures (Tg) for the controlled architecture polymers typically arefrom about −60° C. to about −35° C. However, it will be appreciated thatthe polymers of the present subject matter can exhibit Tg's outside ofthis range such as less than −60° C. and/or greater than −35° C.

In certain embodiments, the present subject matter utilizes a two-steppolymerization process for making a crosslinkable acrylic copolymerhaving a first segment with reactive functional groups provided by atleast one acrylic monomer. A second segment is added to the firstsegment to form the acrylic copolymer. The second segment does notcontain crosslinkable functional groups and is miscible with the firstsegment.

The reactive segment of the acrylic polymer may be a copolymer derivedfrom one or more of the monomers of the non-reactive segment and atleast one polymerizable comonomer having crosslinkable functionality. Inone embodiment, the reactive segment comprises at least one monomerhaving the formula:

where R is H or CH₃ and X represents or contains a functional groupcapable of crosslinking. The crosslinkable functional group of thereactive segment of the acrylic polymer is not particularly restricted,but may include one or more crosslinkable silyl, hydroxyl, carboxyl,carbonyl, carbonate ester, isocyanato, epoxy, vinyl, amino, amide,imide, anhydride, mercapto, acid, acrylamide and acetoacetyl groups.

Hydroxy functional monomers include, for example, hydroxyl ethyl(meth)acrylate, hydroxyl isopropyl (meth)acylate, hydroxyl butyl(meth)acrylate and the like. Epoxy functional monomers include, forexample, glycidyl methacrylate and glycidal acrylate.

The acid containing monomers include unsaturated carboxylic acidscontaining from 3 to about 20 carbon atoms. The unsaturated carboxylicacids include, among others, acrylic acid, methacrylic acid, itaconicacid, beta carboxy ethyl acrylate, mono-2-acroyloxypropyl succinate, andthe like. Anhydride containing monomers include maleic anhydride,itaconic anhydride, citraconic anhydride and the like.

The acrylamides include acrylamide and its derivatives including theN-substituted alkyl and aryl derivatives thereof. These include N-methylacrylamide, N,N-dimethyl acrylamide, t-octyl acrylamide and the like.The methacrylamides include methacrylamide and its derivatives includingthe N-substituted alkyl and aryl derivatives thereof. The vinyl estersinclude vinyl acetate, vinyl propionate, vinyl butyrate, vinyl valerate,vinyl versitate, vinyl isobutyrate and the like. The vinyl ethersinclude vinyl ethers having 1 to about 8 carbon atoms includingethylvinyl ether, butylvinyl ether, 2-ethylhexylvinyl ether and thelike. The vinyl amides include vinyl amides having 1 to about 8 carbonatoms including vinyl pyrrolidone, and the like. The vinyl ketonesinclude vinyl ketones having 1 to about 8 carbon atoms includingethylvinyl ketone, butylvinyl ketone, and the like.

The polymerizable silanes include vinyltrimethoxysilane,vinyltriethoxysilane, vinyltripropoxysilane, vinylmethyldimethoxysilane,vinylmethyldiethoxy-silane, vinylmethyldipropoxysilane,γ-methacryloxypropyl-trimethoxysilane,γ-methacryloxypropyltriethoxysilane,γ-methacryloxypropyl-tripropoxysilane, γ-methacryloxydimethoxysilane,γ-methacryloxypropyl-methyldimethoxysilane,γ-methacryloxypropylmethyldiethoxysilane,γ-methacryl-oxypropylmethyldipropoxysilane,γ-methacryloxymethyl-dimethoxysilane,γ-methacryloxymethyltrimethoxysilane,γ-methacryloxymethyl-triethoxy-silane, (methacryloxymethyl)methyldimethoxysilane, (methacryloxymethyl)-methyldiethoxysilane,γ-methacryloxypropyltriacetoxysilane, γ-acryloxypropyltrimethoxy-silane,γ-acryloxypropyltriethoxy-silane, γ-methacryl-oxymethyldiethoxysilane,γ-acryloxypropyltripropoxy-silane,γ-acryloxypropyl-methyldimethoxysilane,γ-acryloxypropylmethyldiethoxysilane,γ-acryloxypropyl-methyldipropoxysilane, and the like.

In addition to the monomer having functional group(s), the reactivesegment may include at least one monomer having the formula:

where R₃ is H or CH₃ and R₄ is a branched or unbranched, saturated alkylgroup having 4 to 14 carbon atoms.

In one embodiment, the reactive segments include about 40% to about 99%by weight of the one or more monomers of the non-reactive segments. Inanother embodiment, the reactive segments include about 50% to about 99%by weight of the one or more monomers of the non-reactive segments. Inanother embodiment, the reactive segments include about 60% to about 99%by weight of the one or more monomers of the non-reactive segments. Inanother embodiment, the reactive segments include about 70% to about 99%by weight of the one or more monomers of the non-reactive segments. Inanother embodiment, the reactive segments include about 80% to about 99%by weight of the one or more monomers of the non-reactive segments. Inanother embodiment, the reactive segments include about 90% to about 99%by weight of the one or more monomers of the non-reactive segments. Inanother embodiment, the reactive segments include less than about 40% byweight of the one or more monomers of the non-reactive segments. Inanother embodiment, the reactive segments include more than about 99% byweight of the one or more monomers of the non-reactive segments.

As used herein, the term “molecularly miscible” means a compound ormixture of compounds that exhibit properties in the bulk state that canbe observed and/or measured by one of ordinary skill in the art and areindicative of single phase behavior. The term “single phase behavior”refers to behavior or physical properties that are uniform orsubstantially so. With respect to the acrylic copolymer, the observationof a single Tg is indicative of polymer segment miscibility. The singleTg is intermediate between those of the constituent polymer segments andvaries monotonically between these values as the relative amounts ofeach segment changes. In contrast to single phase behavior evidenced bya molecularly miscible compound or mixture of compounds, at a giventemperature, a phase separated compound demonstrates multiple,independent sets of properties that are attributable to the differentphases of matter present therein. Such sets of properties include,without limitation, T_(g), solubility parameters, refractive index, andphysical state/phase of matter. Accordingly, the term “phase separated”is defined as two or more substances which are molecularly segregateddue to one or more chemical and/or physical properties dependent upon,without limitation, polarity, molecular weight, relative amounts of thepolymer segments, and T_(g) (phase of matter).

Evidence of immiscibility/incompatibility between blocks/segments of ablock copolymer, such as an ABA block copolymer, can be confirmed viarheological measurements such as Dynamic Mechanical Analysis (DMA) orDifferential Scanning Calorimetry (DSC) and the microstructuredetermined from microscopy. Miscible polymers exhibit no heterogeneity(i.e., are single phase polymers) in their microstructure. The degree ofmiscibility/compatibility of a polymer blend can be simply determined bymeasuring the glass transition temperature(s) in a DMA or DSC can. Thepresence of two Tgs indicates immiscibility, while the presence of onlya single Tg indicates a miscible blend. For block copolymers withmutually incompatible blocks, the microdomains formed by the differentblocks exhibit separate/different Tgs, and for incompatible blockcopolymers separate Tg values are also observed in the DMA and/or DSCplots. For example, for typical styrenic and acrylic ABA blockcopolymers, the hard A block and the soft B block have sufficientlydifferent solubility parameters such that they are not thermodynamicallycompatible with each other. As a result, block copolymer-based adhesiveshave a unique microphase-separated morphology, where A blocks form ahard phase embedded in a soft, continuous phase composed of B blocks.That is, a result of the frequent immiscibility/incompatibility of thetwo types of blocks present in ABA block copolymers, block copolymersgenerally exhibit two distinct glass transitions (a DMA bimodal tan δcurve) at temperatures very close to those of the correspondinghomopolymers. The presence of acid, however, in block copolymers such asP(MMA/MAA)-PBA-P(MMA/MAA) raises the Tg of the end block and alsoenhances the phase separation between the soft acrylate and the hardPMMA domains. Therefore, block copolymers can exhibit morphologies whichrange from two-phase segregated materials to single-phase homogeneousmaterials.

Additional details of the controlled architecture polymers includingtheir syntheses are described in the noted commonly-owned applicationsUS 2011/0118372; US 2013/0059971; and US 2014/0329958.

In many embodiments of the present subject matter the CAPs utilized inthe adhesives exhibit particular distributions of reactive functionalgroups within the polymer. In various embodiments, at least 80% of thereactive functional groups are located within the end blocks or terminalends of the polymer. For purposes of this disclosure, the terms “endblocks” or “terminal blocks” of the polymer refer to end segments of thepolymer. These end blocks or terminal ends have a molecular weight lessthan 50,000 g/mol; in particular embodiments, the molecular weight maybe less than 30,000 g/mol, while in still additional particularembodiments, the molecular weight of the end blocks may be less than10,000 g/mol.

The remaining portion of the reactive functional groups, i.e., up to20%, are located within one or more interior region(s) of the polymer.In particular embodiments, at least 90% of the reactive functionalgroups are located within the end blocks or terminal ends and theremaining portion, i.e., up to 10%, is located within one or moreinterior regions of the polymer. In still other embodiments, at least95% of the reactive functional groups are located within the end blocksor terminal ends of the polymer. The remaining portion of the reactivefunctional groups, i.e., up to 5%, are located within one or moreinterior region(s) of the polymer. And in specific embodiments, at least99% of the reactive functional groups are located within the end blocksor terminal ends and the remaining portion, i.e., up to 1%, is locatedwithin one or more interior regions of the polymer.

As previously noted, upon crosslinking of the present subject matteradhesives and formation of an enhanced terminally linked polymericnetwork, the resulting enhanced adhesive exhibits certain propertiesthat are at least comparable to, and in many instances superior to,those of adhesives utilizing conventional randomly crosslinked polymericnetworks. FIG. 1 is a schematic illustration depicting a conventionalpolymer including various reactive functional groups and upon exposureto UV radiation, formation of a conventional randomly crosslinkednetwork. In FIG. 1, the various functional groups are schematicallyrepresented by the vertical line segments located along the polymerchain or backbone which is represented by the horizontal line segment.Upon crosslinking, crosslink bonds involve interior regions of thepolymers as a result of many functional groups being located withinthose interior regions. FIG. 2 is a schematic illustration depictingcontrolled architecture polymers (CAPs) and upon exposure to UVradiation, formation of an enhanced terminally linked network inaccordance with the present subject matter. The CAPs include variousfunctional groups located primarily at or near terminal ends of thepolymers. Thus, upon crosslinking, the network that forms ischaracterized by crosslink bonds primarily at terminal ends of thepolymers, and an absence or a relatively minor extent of crosslink bondsinvolving interior regions of the polymers.

The resulting polymeric networks influence and in many regards determinephysical properties of the resulting adhesives. FIG. 3 is a schematicillustration of a conventional randomly crosslinked network and, uponincorporation in an adhesive, typical adhesive properties associatedwith such network. FIG. 4 is a schematic illustration of an enhancedterminally linked network and, upon incorporation in an adhesive,typical adhesive properties associated with such network in the adhesivein accordance with the present subject matter. While the graphs in FIGS.3 and 4 do not contain values on the y-axis, each graph is presentedwith the same scale. Accordingly, the networked polymer created thoughcontrolled architecture polymerization and depicted in FIG. 4demonstrates both an improved peel strength (pounds per linear inch) andshear strength (minutes) when compared to the randomly crosslinkednetwork depicted in FIG. 3.

Non-CAPs

In certain embodiments, the melt processable, actinic radiationpolymerizable and crosslinkable adhesives of the present subject matterare produced from polymers that are not controlled architecturepolymers, or as referred to herein as “non-CAPs.” Such adhesives arefree of controlled architecture polymers.

In many applications involving non-CAP based adhesives, the polymers areacrylic or alkyl acrylate polymers.

The alkyl acrylates and alkyl methacrylates used in the present subjectmatter include straight chain alkyl groups, branched chain alkyl groups,or cyclic alkyl groups and, in many embodiments contain from 1 to about24 carbon atoms. In particular embodiments, the alkyl group containsfrom 1 to about 12 carbon atoms.

In a particular embodiment, the alkyl acrylate or alkyl methacrylatemonomers have from about 4 to about 8 carbon atoms. Such monomers aregenerally commercially available as commodity chemicals and are lessexpensive than longer chain alkyl acrylates and methacrylates. They alsotend to yield copolymers having a good balance of tack and peel.

A representative, but nonlimiting list of alkyl acrylates and alkylmethacrylates useful in the practice of the present subject matterincludes methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropylacrylate, n-butyl acrylate, isobutyl acrylate, n-amyl acrylate, isoamylacrylate, n-hexyl acrylate, isohexyl acrylate, cyclohexyl acrylate,isooctyl acrylate, 2-ethylhexyl acrylate, decyl acrylate, laurylacrylate, stearyl acrylate, isobornyl acrylate, and mixtures thereof, aswell as the analogous methacrylate monomers. It will be appreciated,however, that alkyl methacrylates generally yield copolymers havinghigher Tg's than their alkyl acrylate counterparts. Therefore, whenalkyl methacrylates are used, they are employed in small quantitiesonly. As a general rule of thumb, the alkyl methacrylates comprise nomore than about 15% of the total weight of all monomers.

The non-CAP polymer(s) include one or more reactive functional groups asdescribed herein in association with the CAPs. However, the one or morereactive functional groups can be incorporated along the polymer chainor backbone in a non-structured or random or non-ordered manner.

Representative and non-limiting examples of ranges of glass transitiontemperatures (Tg) for the non-CAP polymers typically are from about −60°C. to about −35° C. However, it will be appreciated that the polymers ofthe present subject matter can exhibit Tg's outside of this range suchas less than −60° C. and/or greater than −35° C.

It is also contemplated that the present subject matter may includecombinations or blends of CAPs and non-CAPs.

Methods

In many embodiments, the present subject matter provides methods offorming an adhesive. The methods comprise providing a compositionincluding at least one monomer having one or more ethylenicallyunsaturated bonds, a first actinic radiation initiator, and a secondactinic radiation initiator, wherein the second initiator issubstantially non-photoactive at activation wavelength(s) of the firstinitiator. The methods also comprise at least partially polymerizing thecomposition by exposing the composition to radiation having wavelengthscorresponding to the activation wavelength(s) of the first initiator.The methods additionally comprise at least partially crosslinking thecomposition to thereby form the adhesive by exposing the composition toradiation having wavelengths corresponding to the activationwavelength(s) of the second initiator. In these methods the compositionis free of solvents.

In still other embodiments, the present subject matter providesadditional methods of forming an adhesive. The methods compriseproviding a composition including at least one monomer, a first actinicradiation initiator, and a second actinic radiation initiator, whereinthe second initiator is substantially non-photoactive at activationwavelength(s) of the first initiator. The methods also comprise at leastpartially polymerizing the composition by exposing the composition toradiation having wavelengths corresponding to the activationwavelength(s) of the first initiator. The methods additionally compriseat least partially crosslinking the composition to thereby form theadhesive by exposing the composition to radiation having wavelengthscorresponding to the activation wavelength(s) of the second initiator.At least one of the first and the second initiators is a polymer havinga photoinitiator moiety along the polymer backbone.

The present subject matter also provides methods of forming a meltprocessable, actinic radiation polymerizable and crosslinkable adhesive.In many embodiments, the methods utilize controlled architecturepolymers that include at least one reactive functional group. In certainembodiments, at least 80% of the reactive functional groups are locatedwithin terminal ends of the polymer. The methods also comprise providingtwo or more initiators as described herein. The methods additionallycomprise blending the polymers, which as noted may be controlledarchitecture polymers, with the initiators to thereby form apre-adhesive composition.

The present subject matter also provides methods of forming actinicradiation polymerizable and crosslinkable melt adhesives using non-CAPbased polymers as described herein. In these embodiments, the methodscomprise providing nonstructured polymers that include one or morereactive functional groups. The methods also comprise providing two ormore initiators capable of polymerizing and crosslinking thecomposition. The methods also comprise blending the polymers with theinitiators to thereby form a pre-adhesive composition. The methodsadditionally comprise exposing the composition to actinic radiation fora time period and at an intensity in a first stage sufficient to atleast partially polymerize the composition. The methods also compriseexposing the composition for a time period and at an intensity in asecond stage sufficient to crosslink the composition and thereby formthe adhesive.

The present subject matter adhesives or compositions are polymerizedand/or crosslinked by exposure to actinic radiation, and particularlyultraviolet (UV) radiation or near UV radiation. As previously noted,electron beam radiation can also be used. As will be appreciated,sufficient exposure to such radiation causes polymerization and/orcrosslinking involving various functional groups incorporated in thepolymers and in certain embodiments the CAPs.

Use of the two stage methods described herein enable formation of apre-adhesive formulation that can be further processed by subsequent oradditional exposure to actinic radiation and particularly UV radiation.Thus, an initial batch or a desired amount of pre-adhesive can bepolymerized or at least partially polymerized in bulk and then stored orheld for later application or coating to a substrate of interest.

After the adhesive is coated on a substrate at a desired coat weight,the coated substrate is irradiated with actinic radiation andparticularly UV radiation to yield a crosslinked adhesive and in manyembodiments a pressure sensitive adhesive having high cohesive strengthat room and elevated temperatures. A variety of UV light sources areknown, including low, high, and medium pressure mercury lamps, whichemit over a wide range of wavelengths. Most pigmented and unpigmentedadhesives can be readily cured using a medium pressure mercury lamp,which has emission bands ranging from about 240 to about 410 nanometers.Alternatively, UV sources that emit over a more narrow range ofwavelengths can be used if desired, so long as the emission spectrum ofthe source overlaps with the absorption spectrum of the initiator(s)employed within the adhesive. Where the adhesive is pigmented withtitanium dioxide or similar pigments, the preferred initiator hasabsorption bands in the near UV region, and a UV source that emits atleast in that region is employed.

As noted, in particular embodiments, the methods of the present subjectmatter involve the use of one or both of the initiators being in theform of polymerizable monomers. The methods involve incorporation and/orpolymerization of the first and/or second initiators into the polymersconstituting the adhesive.

FIG. 5 is a process schematic diagram depicting a representative processand system 10 for producing an adhesive and polymerizing andcrosslinking the adhesive in accordance with the present subject matter.The system 10 generally comprises a dispenser or heater 12 forintroducing one or more adhesives, polymers, and/or monomers via feedline 14 to a blender or mixer 22. Also provided are additional feedlines 16, 18, and 20 which can be for selectively metering desiredamounts of a first initiator, a second initiator, and ancillarycomponents or other additives to the mixer 22. It will be appreciatedthat the first and/or second initiator can be introduced in the form ofpolymerizable monomers which are polymerized with or separately frommonomers) that form the adhesive.

After appropriate mixing of the adhesive, polymers and/or monomers,photoinitiators, and optional components, the resulting pre-adhesive isdirected through line 24 to a reactor 26 which can be in the form of atube reactor for example. The reactor 26 can be in a variety ofdifferent forms however typically defines an interior region forreceiving adhesive or pre-adhesive. The reactor 26 is configured toallow actinic radiation such as UV radiation to enter the interior ofthe reactor from one or more radiation sources as described herein. Theadhesive is directed through the reactor 26 and exposed in a first stageto actinic radiation from UV emitters 28, 30 that emit UV light orradiation shown as rays 29, 31 for example, having a wavelengthcorresponding to an activation wavelength of one of the initiators andtypically the first initiator. The flow rate, i.e., residence time ofadhesive in the reactor 26; intensity of the UV light; and other factorsare adjusted to produce a partially or fully polymerized adhesiveexiting the reactor 26 via line 32. Polymerization between monomer(s)primarily occurs in the reactor 26.

The adhesive in line 32 may be directly deposited or applied to one ormore substrates on a moving web 42 (typically driven by rotating roller40) via line 34, or directed via line 36 to a storage unit 44 foradditional processing and/or subsequent application.

Upon deposition of the adhesive shown in FIG. 5 as regions 45, theadhesive typically on the moving web 42, is irradiated by another UVemitter in a second stage 50 that directs UV rays 51 upon the regions 46to crosslink the adhesive. Crosslinked adhesive 52 results.

In particular embodiments, two or more conventional medium pressuremercury lamps can be used having spectral emissions from about 240 toabout 410 nanometers, and light intensities of from about 5 to 10kWatts/m². Nonlimiting examples of UV light intensities for processingadhesives of the present subject matter can range from about 0.1 toabout 100 kWatts/m², in certain embodiments from 1 to 50 kWatts/m², andin particular embodiments from 1 to 20 kWatts/m². The coated substrateis carried on a moving web under or near the UV radiation source, wherethe web temperature may range from 45° C. to 125° C. The dosage of UVradiation received by the coated adhesive film is controlled byadjusting the UV lamp intensity and/or the web speed. Nonlimitingexamples of time periods for processing adhesives of the present subjectmatter are typically less than 60 minutes, more typically less than 10minutes, in many embodiments less than 1 minute, and in particularembodiments less than 10 seconds.

Upon exposing adhesive to the noted conditions, if the adhesive includesCAPs, the adhesive then includes an ETLN. As previously described, theETLN adhesives of the present subject matter exhibit an array ofadvantages and benefits and particularly when compared tonon-architecture polymers which produce randomly crosslinked networks.

Specifically, as shown in FIG. 6, a method 60 includes providing a meltadhesive having (i) a first UV photoinitiator for bulk curing of theadhesive, and (ii) a second UV photoinitiator for on-web crosslinking ofthe adhesive. The second photoinitiator is substantially non-photoactiveat activation wavelengths of the first photoinitiator. This is depictedas one or more operations 65 in FIG. 6. The methods also include atleast partially curing the adhesive by irradiating the adhesive with UVlight having wavelengths corresponding to the activation wavelengths ofthe first photoinitiator. This is shown as one or more operations 70 inFIG. 6. The methods additionally include applying the at least partiallycured adhesive to a surface of interest. And, the methods includecrosslinking the adhesive shown as operation(s) 75 by irradiating theadhesive with UV light having wavelengths corresponding to theactivation wavelengths of the second photoinitiator, to thereby form theadhesive at 80. It will be appreciated that the present subject matterincludes the use of initiators activated by exposure to electron beamradiation instead of, or in addition to, either or both of the first andsecond UV photoinitiator(s).

As will be understood, during conversion of the composition(s) of thepresent subject matter from a pre-adhesive to a pressure sensitiveadhesive, in many embodiments, the modulus of the composition changeswhile the glass transition temperature (Tg) does not change or remainssubstantially the same.

Optical Filters

Another aspect of the present subject matter involves selective exposureof UV radiation having a desired wavelength or range of wavelengths toone or both of the UV photoinitiators at particular times or processphases. For example, in one embodiment of the present subject matter,one or more optical filters can be used to selectively filter and/orblock UV radiation of particular wavelength(s). Using this technique,adhesive or pre-adhesive can be exposed to a UV radiation source thatactivates the first UV photoinitiator yet which does not activate thesecond photoinitiator. In this version of the present subject matter,one or more optical filters are used to selectively block UV radiationhaving wavelength(s) corresponding to the activation wavelength(s) ofthe second photoinitiator. The present subject matter also includes theuse of optical filters to selectively filter and/or block particularradiation wavelength(s) that correspond to the activation wavelength(s)of the first photoinitiator.

A wide array of materials and equipment can be used to provide the notedoptical filter(s). The optical filter(s) are positioned between the UVradiation source and the adhesive or pre-adhesive. Referring to FIG. 5again, the one or more optical filters can be disposed or otherwisepositioned between the UV emitter 28 and the reactor 26 so that the UVradiation 29 passes through the filters. Similarly, one or more opticalfilters could be positioned between region(s) 46 and the second stage50. In many embodiments, the optical filters include particularpolymeric layers, lenses, and/or films that are formulated to allowpassage of certain wavelengths and block passage of other wavelengths.Nonlimiting examples of such materials include polycarbonates such asthose commercially available under the LEXAN® designation, certainpolyethylene terephthalates, certain polymethyl methacrylates (PMMAs),and combinations thereof. It is also contemplated to utilize one or moredichroic glasses as the optical filters described herein. It will beunderstood that the present subject matter is not limited to any ofthese particular materials. Instead, the subject matter includes a widearray of materials and assemblies for selectively filtering and/orenabling passage of electromagnetic radiation having desiredwavelength(s) to the adhesive or pre-adhesive.

The optical filter(s) can be configured to block or otherwise preventpassage of electromagnetic radiation and in particular UV radiationhaving particular wavelength(s). In many embodiments, the opticalfilters block passage of UV radiation having wavelength(s) correspondingto the activation wavelength(s) of the second photoinitiator. Aspreviously noted, in certain embodiments of the present subject matterthe activation wavelengths of the second photoinitiator are within arange of from 100 nm to 500 nm, and particularly from 200 nm to 375 nm.

The optical filter(s) can be configured such that they can beselectively positioned between one or more light sources and theadhesive or process component(s) containing the adhesive or pre-adhesivesuch as a reactor. The optical filter(s) can also be configured so thatthe filter(s) can be moved to thereby allow passage of light in anunfiltered or unblocked manner.

If multiple light sources are used, the present subject matter includesthe use of optical filter(s) associated with some or all of the lightsources. The present subject matter includes a wide array of processcomponents and system configurations.

Articles

The present subject matter provides a wide array of articles thatinclude the noted compositions, pre-adhesives, and/or adhesives.Examples of such articles include adhesive tapes including double sidedand single sided tapes; label stock; label constructions; packagingproducts and assemblies including food packages, packaging for householdgoods and industrial goods and particularly reclosable packages; andother items.

FIG. 7 illustrates a tape article 100 in accordance with an embodimentof the present subject matter. The tape article 100 is shown in a rollform, however, it will be appreciated that the tape could be in a flat,sheet, or Z-fold form. The tape article 100 generally includes asubstrate 110 defining a first face 112 and an oppositely directedsecond face 114. The tape 100 includes a layer or region of an adhesiveas described herein disposed on one or both faces 112, 114. One or morerelease liners and/or low surface energy coatings can be used asdescribed in greater detail herein.

FIG. 8 is a schematic cross sectional view of a tape 100A comprising asubstrate 110 defining a first face 112 and an oppositely directedsecond face 114. The tape 100A also comprises a layer or region of anadhesive 120 disposed on one of the faces such as for example face 114.One or more low surface energy coatings can be disposed on the face 112of the substrate 110.

FIG. 9 is a schematic cross sectional view of a tape 100B comprising asubstrate 110 defining a first face 112 and an oppositely directedsecond face 114. The tape 100B also comprises a layer or region of anadhesive 120 disposed on one of the faces such as for example face 114.The tape 100B also comprises a release liner 130 covering the adhesive120. One or more low surface energy coatings can be disposed on the face112 of the substrate 110.

FIG. 10 is a schematic cross sectional view of a tape 100C comprising asubstrate 110 defining a first face 112 and an oppositely directedsecond face 114. The tape 100C also comprises a first layer or region ofan adhesive 120 disposed on one of the faces such as for example face114. The tape 100B also comprises a second layer or region of anadhesive 125 disposed on the face 112 of the substrate 110.

FIG. 11 is a schematic cross sectional view of a tape 100D comprising asubstrate 110 defining a first face 112 and an oppositely directedsecond face 114. The tape 100D also comprises a first layer or region ofan adhesive 120 disposed on one of the faces such as for example face114. The tape 100D also comprises a second layer or region of anadhesive 125 on the face 112. The tape 100D also comprises a firstrelease liner 130 covering the adhesive 120. And, the tape 100Dadditionally comprises a second release liner 135 covering the adhesive125.

FIG. 12 is a schematic cross sectional view of a sealing, closure, orreclosure assembly 200 in accordance with the present subject matter.This assembly comprises a first substrate 210 defining a first substrateface 212, a second substrate 230 defining a second substrate face 214,and one or more layers or regions of an adhesive 220 defining anadhesive face 222. The adhesive 220 is disposed on one or both substratefaces 212, 214. The adhesive 220 serves to seal and/or adhere thesubstrates 210, 230 together upon contact between the adhesive face 222and the substrate face 212. As will be understood, the adhesive 220 isany of the adhesives described herein. The assembly 200 can be utilizedin association with and/or incorporated in a wide array of packagingproducts including for example food packages, packages for householdgoods, industrial goods packages, and in particular recloseablepackages.

The adhesive layer may have a thickness as desired for a particularpurpose or intended use. In one embodiment, the adhesive layer may havea thickness from about 10 to about 125, or from about 10 to about 75, orfrom about 10 to about 50 microns. In one embodiment, the coat weight ofthe adhesive may be in the range of about 10 to about 50 grams persquare meter (gsm), and in one embodiment about 20 to about 35 gsm.

Release liners for use in the present subject matter may be those knownin the art or those later discovered. In general, suitable releaseliners include, but are not limited to, polyethylene coated papers witha commercial silicone release coating, polyethylene coated polyethyleneterephthalate films with a commercial silicone release coating, or castpolypropylene films that can be embossed with a pattern or patternswhile making such films, and thereafter coated with a commercialsilicone release coating. An exemplary release liner is kraft paperwhich has a coating of low density polyethylene on the front side with asilicone release coating and a coating of high density polyethylene orpolypropylene on the back side. Other release liners known in the artare also suitable as long as they are selected for their releasecharacteristics relative to the pressure sensitive adhesive chosen foruse in the adhesive article, that is, the adhesive will have a greateraffinity for the face stock than the liner.

As previously noted, one or more low surface energy coatings can be usedin the articles utilizing the adhesives described herein. For example,for rolled tape products it may be desirable to provide a coating of alow surface energy agent along a rear face of a substrate or tapecomponent that contacts the adhesive. Nonlimiting examples of lowsurface energy coatings include silicone agents, polypropylene or otherpolyolefins, certain fluorocarbons, and certain fatty acid esters.

A benefit of particular adhesives of the present subject matter involvesmaintenance of performance criteria upon continued exposure to UVradiation. For example, a disadvantage of many conventional UV cured,randomly crosslinked adhesive networks is that additional UV exposureresults in additional crosslinking. This may in turn result inundesirable changes in the adhesive and/or its performance.Specifically, this may be undesirable for clear or transparent labelsthat are UV printed downstream. In contrast, many embodiments of thepresent subject matter adhesives do not exhibit performance changes uponadditional UV exposure.

Additional Aspects

FIG. 13 schematically illustrates an apparatus for polymerizing orcrosslinking adhesives by exposure to actinic radiation using one ormore light emitting probes. Specific wavelengths of radiation emitted atspecific angles and heights relative to an upper surface of an adhesiveor pre-adhesive contained within the apparatus are used to achievevarying polymer properties. FIG. 13 shows three of four positions ofirradiation: surface, angled surface, sub-surface, and angledsub-surface. Probes can be attached to the side, top, or bottom of areaction vessel and are held in place via pressure rated sealing andlocking collars. This provides further flexibility to the penetrationdepth of each probe. A typical configuration for individual probes isone in which each probe comprises a pressure rated light tube, LEDemitter, and a Class 1/Division 1 enclosure with integrated heat sink.The light controller/driver is located remotely. The probe isconstructed with a smoothed, polished interior wall that reflectsradiation from the source and emits the radiation through the tip of theprobe within the reaction vessel. Materials that are transparent to theradiation wavelengths are used at the probe's tip. Nonlimiting examplesof such materials include glass, quartz, sapphire, and similarmaterials. In many embodiments, the complete apparatus is certified tomeet or exceed pressure and temperature ratings of the chosen reactionvessel. In addition to LED, other light sources can be considered alongwith other ancillary apparatus components such as power source, coolingprovisions and the like.

Specifically, referring to FIG. 13, an apparatus 300 for polymerizingand/or crosslinking an adhesive or pre-adhesive composition is shown.The apparatus comprises a reaction vessel 320 defining an interiorchamber 322 for the composition. The vessel 320 typically includesstirring or mixing provisions 340, one or more drain ports 350, andassociated valving 352 to govern entry and exit of flow(s) to the vessel320. An optional heating and/or cooling jacket 370 may be provided alongexterior regions of the vessel 320. The apparatus 300 also comprises oneor more probe assemblies 310 engaged with the reaction vessel 320 viacollar(s) 330. The collar 330 provides access to the interior chamber322 of the vessel 320 and is located along an upper region of the vessel320 typically within a top wall of the vessel 320. The collar 320includes provisions for releasably engaging a probe assembly 310 andsupporting the probe assembly relative to the vessel 320. The probeassembly 310 includes an emitter 312, a light tube 314 extending fromthe emitter, optional heat sink provisions 318 associated with theemitter 312, and adjustable positioning provisions 316. The light tube314 defines a distal end 315 opposite the emitter 312. In manyembodiments, a probe assembly 310 is disposed relative to the reactionvessel 320 such that the emitter 312 is positioned above the vessel 320,and the light tube 314 extends into the interior chamber 322 of thevessel 320 through the collar 330. The adjustable positioning provisions316 are engaged or associated with the light tube 314 and serve togovern and/or maintain a desired position of the light tube 314 withinthe chamber 322. FIG. 13 depicts various positions of the light tube 314relative to the vessel 320 and specifically, an upper surface 302 of anadhesive or pre-adhesive composition contained within the vessel 320.For example, probe assembly 310A includes an emitter 312A, a light tube314A extending into the interior chamber 322 of the vessel 320, andadjustable positioning provisions 316A. Probe assembly 310A is depictedin an angled sub-surface position as the light tube 314A is at anon-vertical orientation and the distal end 315A of the light tube 314Ais below the upper surface 302 of the composition contained within thevessel 320. Probe assembly 310B includes an emitter 312B, a light tube314B extending into the chamber 322, and adjustable positioningprovisions 316B. Probe assembly 310B is depicted in sub-surface positionas the light tube 314B is at a vertical orientation and the distal end315B of the light tube 314B is below the upper surface 302. Probeassembly 310C includes an emitter 312C, a light tube 314C extending intothe chamber 322, and adjustable positioning provisions 316C. Probeassembly 310C is shown in an angled surface position as the light tube314C is at a non-vertical orientation and the distal end 315C of thelight tube 314C is above the upper surface 302. As will be appreciated,a surface position for a probe assembly corresponds to a light tubeoriented at a vertical position and having a distal end of the lighttube positioned above the upper surface.

The apparatus 300 can include a single probe assembly or multiple probeassemblies. And, the probe assemblies can be located proximate oneanother as shown in FIG. 13, or the probe assemblies can be locatedalong different regions of the vessel such as one or two or more locatedalong a top region, and one or two or more located along side region(s)of the vessel.

The emitter 312 of a probe assembly 310 typically includes one or moreemitter(s) of actinic radiation such as a light source. The emitter 312can optionally include heat dissipating provisions such as an integratedheat sink 318 located along exterior region(s) of the emitter 312. Aswill be understood each emitter is in communication with a signal and/orpower unit 360. One or more signal/power communication(s) 362 extendbetween the emitter 312 and the signal/power unit 360.

In certain embodiments, the interior wall of a light tube, such as lighttubes 314A, 314B, and/or 314C, provides a smooth, polished surface thatpromotes reflection of light emitted from the emitter. And, in manyembodiments, one or more transparent covers 317 are provided at orproximate the distal end 315 of the light tube 314. As noted, the coveris transparent or substantially transparent to the passage of lightemitted from the emitter and reflected along a length or length portionof the light tube. The term “substantially transparent” as used hereinrefers to the cover having optical properties that enable at least 90%of light emitted from the emitter 312 and reflected along the lighttube, to pass through the cover 317.

An advantage of mounting a probe in a nozzle in the top (also known as“head of the vessel”) is that the probe can be removed withoutdraining/releasing the contents of the vessel. Another advantage ofmounting a probe above the upper surface 302 is that on the outsidevertical walls and bottom walls of the vessel, such walls are typicallycovered with a jackets (i.e., “welded half-pipe”) to provide cooling orheating the contents via thermal conduction. For example, to cool anexothermic reaction, cold water is typically circulated through ahalf-pipe jacket. The presence of the jacket for cooling limits theamount of surface area available and complicates the installation of theprobe through the side-walls and bottom wall.

Another mode of introducing actinic radiation via a probe is through aport, collar, or nozzle incorporated into the vessel below the surfaceof the liquid, either via the side wall or the bottom wall of the vessel(see FIG. 14). This is in contrast to FIG. 13, in which the collar ismounted on the top wall of the vessel. An advantage of mounting theprobe in the bottom wall is that for any fillage of the vessel, theprobe is always submersed. The distance between the probe tip and theliquid is essentially zero, independent of batch size.

Specifically, referring to FIG. 14, another version of the apparatus 300previously described in association with FIG. 13 is shown. In thisversion, a probe assembly 310D is located along a side wall of thereaction vessel 320, and a probe assembly 310E is located along a bottomwall of the vessel 320. Each probe assembly 310D and 310E is engagedwith the vessel 320 by a corresponding collar 330D and 330E. In theparticular version shown in FIG. 14, the distal ends 315D and 315E ofthe light tubes 314D and 314E are flush or substantially flush with aninterior surface of the vessel wall. As previously described,transparent covers 317 are typically located at the light tube distalends, thus, covers 317D and 317E are substantially flush with theinterior wall of the vessel 320.

Yet another mode is to irradiate the contents of the reactor using asight glass built into the side vessel, instead of installing a probethrough a nozzle or port (see FIG. 15). The sight glass is typicallyflush with the side wall of the vessel. An advantage of having a sightglass flush with the side wall of the vessel is that some vessels haveagitator designs that sweep the inside wall of the vessel at a small gap(akin tolerance or distance). A sweeping agitator blade helps promoteheat transfer in viscous materials. Also, if the light is causing areaction to occur near the glass-product interface, the wiping agitatorblade promotes the mixing of viscous, reacted product in the irradiatedzone with lower viscosity material outside the irradiated zone.

Specifically, FIG. 15 illustrates another version of the apparatus 300.This figure depicts additional aspects of the stirring or mixingprovisions 340. As will be understood, many such provisions 340 includea power unit for rotating a shaft generally extending into the interiorchamber 322 of the vessel 320. The provisions 340 typically include oneor more blades or mixing elements extending from the shaft. In thisversion, the reaction vessel includes one or more sight glasses 380incorporated within wall region(s) of the vessel. The sight glass(es)provides visual access to the interior of the vessel. For example, inthe version of FIG. 15, a plurality of sight glasses 380 are provided,i.e., sight glasses 380A, 380B, and 380C. One or more emitter(s) such asemitter 312F can be positioned adjacent a sight glass such as sightglass 380A. Emission of light from the emitter 312F passes through thesight glass 380A to irradiate the contents of the vessel 320. Inaddition or alternatively, one or more emitter(s) such as emitter 312Gcan be positioned adjacent a sight glass such as sight glass 380C, and alight tube such as light tube 314G can be used to direct light from theemitter 312G to the sight glass 380C for irradiation into the chamber322 of the vessel 320. One or more transparent covers can be used,however, such is likely not necessary. As will be appreciated, it isdesired for many applications that the sight glass is transparent orsubstantially transparent to passage of light emitted from the emitter.

Still another mode of introducing radiation is to mount a LED or otherlight source onto a baffle attached to the reactor wall as depicted inFIG. 16. In this vessel type, the contents of the vessel are agitated bya pitched blade turbine. The primary function of the baffle is to divertflow away from the wall of the vessel. If sufficiently strong, theenclosure of the light source could also function as a baffle inaddition to being the light source. Alternatively, the light source canbe mounted on the front side of the baffle with respect to the rotationof the liquid due to the agitator blade. In all these methods, theirradiated material in front of the source would be constantly renewedto allow reacted viscous material to be thoroughly mixed into theoverall reaction mass.

Specifically, referring to FIG. 16, an apparatus 300 is shown havingstirring or mixing provisions 340 in the form of a pitched bladeturbine. One or more emitters 312 are incorporated in a stationarybaffle 390 that is affixed within the interior chamber 322 of the vessel320. One or more supports 392 attached to the vessel wall can be used toaffix the baffle 390 within the vessel 320. It is also contemplated thatthe baffle(s) can extend from support(s) extending through collars inthe wall(s). Although the present subject matter includes baffle(s) 390that emit light in all directions from the baffle, in certain versions auni-directional or substantially so, light emission configuration isused. Typically, such baffles emit light from a single face of thebaffle. That is, the uni-directional light emission baffle 390 ispositioned within the interior chamber 322 of the vessel 320 such thatlight emitted from the baffle 390 is directed toward approaching flow(s)of composition resulting from movement of the blade(s). However, it willbe understood that the present subject matter includes versions in whichthe baffle(s) emits light directed toward flow(s) of compositiontraveling away from the baffle. The baffle(s) can be self-contained andinclude batteries and electronics for powering the emitter(s), and/orreceive signals and/or power remotely. Although a pitched blade turbineis preferred for certain applications, the present subject matterincludes other types of stirring/mixing provisions.

An advantage of subsurface irradiance is that the reaction zone startsimmediately at the probe tip and penetrates a certain distance definedas the “penetration depth”. The “penetration depth” depth depends uponoptical density and on the nature of the material, the appliedirradiance, the spectral output, and the photoinitiator and itsconcentration. If the light source is positioned above the surface andparticulate(s) exist in the headspace above the liquid, the particulatematter may interact with the incoming light. In particular, if liquidfrom the reaction mass is dispersed into the vapor space and forms anaerosol, then polymer may form in the vapor phase. This is undesirablebecause the reaction is no longer homogeneous and also fouls the reactorheadspace and may foul the optic interface and attenuate theirradiation. Also, the operator can not view the reaction as well with adirty sight glass. Also, clean up of the vessel is difficult after thereaction.

Many other benefits will no doubt become apparent from futureapplication and development of this technology.

All patents, applications, standards, and articles noted herein arehereby incorporated by reference in their entirety.

The present subject matter includes all operable combinations offeatures and aspects described herein. Thus, for example if one featureis described in association with an embodiment and another feature isdescribed in association with another embodiment, it will be understoodthat the present subject matter includes embodiments having acombination of these features.

As described hereinabove, the present subject matter solves manyproblems associated with previous strategies, systems and/orcompositions. However, it will be appreciated that various changes inthe details, materials and arrangements of components, which have beenherein described and illustrated in order to explain the nature of thepresent subject matter, may be made by those skilled in the art withoutdeparting from the principle and scope of the claimed subject matter, asexpressed in the appended claims.

What is claimed is:
 1. A method of forming an adhesive, the methodcomprising: providing a composition including at least one monomerhaving one or more ethylenically unsaturated bonds, a first actinicradiation initiator, and a second actinic radiation initiator, whereinthe second initiator is substantially non-photoactive at activationwavelength(s) of the first initiator; at least partially polymerizingthe composition by exposing the composition to radiation havingwavelengths corresponding to the activation wavelength(s) of the firstinitiator; at least partially crosslinking the composition to therebyform the adhesive by exposing the composition to radiation havingwavelengths corresponding to the activation wavelength(s) of the secondinitiator; wherein the composition is free of solvents.
 2. The method ofclaim 1 whereby the at least partially polymerizing the composition isperformed by irradiating the composition with UV radiation.
 3. Themethod of claim 1 whereby the at least partially polymerizing thecomposition is performed by irradiating the composition with electronbeam radiation.
 4. The method of claim 1 whereby the at least partiallycrosslinking the composition is performed by irradiating the compositionwith UV radiation
 5. The method of claim 1 whereby the at leastpartially crosslinking the composition is performed by irradiating thecomposition with electron beam radiation.
 6. The method of claim 1wherein the first initiator is a polymerizable initiator.
 7. The methodof claim 1 wherein the second initiator is a polymerizable initiator. 8.The method of claim 1 wherein the monomer having one or moreethylenically unsaturated bonds is an acrylate monomer.
 9. The method ofclaim 1 whereby the at least partially polymerizing the compositionforms a pre-adhesive composition that includes controlled architecturepolymers including a reactive functional group.
 10. The method of claim9 wherein the controlled architecture polymers exhibit an apportionmentratio of the reactive functional group between two blocks of the polymerwithin a range of from 1.1:1 to 10,000:1.
 11. An adhesive formed by themethod of claim
 1. 12. An article comprising the adhesive of claim 11.13. A method of forming an adhesive, the method comprising: providing acomposition including at least one monomer, a first actinic radiationinitiator, and a second actinic radiation initiator, wherein the secondinitiator is substantially non-photoactive at activation wavelength(s)of the first initiator; at least partially polymerizing the compositionby exposing the composition to radiation having wavelengthscorresponding to the activation wavelength(s) of the first initiator; atleast partially crosslinking the composition to thereby form theadhesive by exposing the composition to radiation having wavelengthscorresponding to the activation wavelength(s) of the second initiator;wherein at least one of the first and the second initiators is a polymerhaving a photoinitiator moiety along the polymer backbone.
 14. Themethod of claim 13 whereby the at least partially polymerizing thecomposition is performed by irradiating the composition with UVradiation
 15. The method of claim 13 whereby the at least partiallypolymerizing the composition is performed by irradiating the compositionwith electron beam radiation.
 16. The method of claim 13 whereby the atleast partially crosslinking the composition is performed by irradiatingthe composition with UV radiation.
 17. The method of claim 13 wherebythe at least partially crosslinking the composition is performed byirradiating the composition with electron beam radiation.
 18. The methodof claim 13 whereby the at least partially polymerizing the compositionforms a pre-adhesive composition that includes controlled architecturepolymers including a reactive functional group.
 19. The method of claim18 wherein the controlled architecture polymers exhibit an apportionmentratio of the reactive functional group between two blocks of the polymerwithin a range of from 1.1:1 to 10,000:1.
 20. An adhesive formed by themethod of claim
 13. 21. An article comprising the adhesive of claim 20.22. A composition comprising: at least one monomer having one or moreethylenically unsaturated bonds; a first actinic radiation initiator forat least partially polymerizing the at least one monomer to form apre-adhesive, the first initiator being activated at a first activationwavelength(s); a second actinic radiation initiator for at leastpartially crosslinking the pre-adhesive, the second initiator beingactivated at a second activation wavelength(s) and the second initiatorbeing substantially non-photoactive at the first activationwavelength(s).
 23. The composition of claim 22 wherein the firstinitiator is activated by exposure to UV radiation.
 24. The compositionof claim 22 wherein the first initiator is activated by exposure toelectron beam radiation.
 25. The composition of claim 22 wherein thesecond initiator is activated by exposure to UV radiation.
 26. Thecomposition of claim 22 wherein the second initiator is activated byexposure to electron beam radiation.
 27. The composition of claim 22wherein upon activation of the first initiator to form the pre-adhesive,the pre-adhesive exhibits a viscosity within a range of from 1,000 cpsto 80,000 cps at a temperature within a range of from 110° C. to 180° C.28. The composition of claim 27 wherein the pre-adhesive exhibits aviscosity within a range of from 30,000 cps to 40,000 cps at atemperature within a range of from 120° C. to 140° C.
 29. Thecomposition of claim 27 wherein the pre-adhesive exhibits a viscositywithin a range of from 40,000 cps to 50,000 cps at a temperature withina range of from 120° C. to 140° C.
 30. The composition of claim 27wherein the pre-adhesive exhibits a viscosity within a range of from1,000 cps to 15,000 cps at a temperature within a range of from 110° C.to 130° C.
 31. The composition of claim 22 wherein the at least onemonomer is an acrylate monomer.
 32. The composition of claim 22 furthercomprising at least one component selected from the group consisting ofpigments, tackifiers, plasticizers, fillers, diluents, inhibitors, andcombinations thereof.
 33. An article comprising the composition of claim22.
 34. An acrylate melt processable pre-adhesive compositioncomprising: at least one acrylate polymer; an actinic radiationinitiator for at least partially crosslinking the polymer, the initiatorbeing a photoinitiator moiety along the polymer backbone; wherein thepre-adhesive composition prior to activation of the initiator exhibits aviscosity within a range of from 1,000 cps to 80,000 cps at atemperature within a range of from 110° C. to 180° C.
 35. Thecomposition of claim 34 wherein the pre-adhesive exhibits a viscositywithin a range of from 30,000 cps to 40,000 cps at a temperature withina range of from 120° C. to 140° C.
 36. The composition of claim 34wherein the pre-adhesive exhibits a viscosity within a range of from40,000 cps to 50,000 cps at a temperature within a range of from 120° C.to 140° C.
 37. The composition of claim 34 wherein the pre-adhesiveexhibits a viscosity within a range of from 1,000 cps to 15,000 cps at atemperature within a range of from 110° C. to 130° C.
 38. Thecomposition of claim 34 wherein the composition includes at least 95%solids.
 39. The composition of claim 34 wherein upon exposure to actinicradiation corresponding to the activation wavelengths of the initiator,the composition is a pressure sensitive adhesive.
 40. The composition ofclaim 34 wherein the at least one acrylate polymer includes alkylacrylate polymers.
 41. The composition of claim 34 wherein the acrylatepolymer is a controlled architecture polymer including a reactivefunctional group.
 42. The composition of claim 41 wherein the controlledarchitecture polymer exhibits an apportionment ratio of the reactivefunctional group between two blocks of the polymer within a range ofform 1.1:1 to 10,000:1.
 43. The composition of claim 41 wherein thecontrolled architecture polymer has a molecular weight within a range offrom 10,000 to 300,000.
 44. The composition of claim 41 wherein thecontrolled architecture polymer has a polydispersity value less than4.0.
 45. An article comprising the composition of claim
 34. 46. Anapparatus for polymerizing and/or crosslinking an adhesive orpre-adhesive composition, the apparatus comprising: a reaction vesseldefining an interior chamber and including at least one collar providingaccess to the interior chamber; at least one probe assembly supported bythe collar, the probe assembly including (i) an emitter for emittinglight that polymerizes and/or crosslinks the composition, (ii) a lighttube extending from the emitter and at least partially disposed withinthe interior chamber of the reaction vessel, (iii) adjustablepositioning provisions for governing position of the light tube withinthe interior chamber of the reaction vessel, and (iv) a cover disposedat a distal end of the light tube, wherein the cover is transparent orsubstantially transparent to passage of light emitted from the emitter.47. The apparatus of claim 46 wherein the probe assembly is positionableto at least one position selected from the group consisting of a surfaceposition, an angled surface position, a sub-surface position, and anangled sub-surface position.
 48. The apparatus of claim 46 wherein theapparatus comprises a single probe assembly.
 49. The apparatus of claim46 wherein the apparatus comprises multiple probe assemblies.
 50. Theapparatus of claim 46 wherein the collar and at least one probe assemblyare located along a top wall of the reaction vessel.
 51. The apparatusof claim 46 wherein the collar and at least one probe assembly arelocated along a side wall of the reaction vessel.
 52. The apparatus ofclaim 46 wherein the collar and at least one probe assembly are locatedalong a bottom wall of the reaction vessel.
 53. The apparatus of claim46 wherein the vessel further includes mixing provisions.
 54. Anapparatus for polymerizing and/or crosslinking an adhesive orpre-adhesive composition, the apparatus comprising: a reaction vesseldefining an interior chamber and at least one sight glass incorporatedin a wall of the vessel and providing visual access to the interiorchamber; at least one probe assembly adjacent the sight glass, the probeassembly including an emitter for emitting light that polymerizes and/orcrosslinks the composition, the probe assembly positioned such thatlight emitted from the emitter is directed to the sight glass and passesinto the interior chamber of the reaction vessel; wherein the sightglass is transparent or substantially transparent to passage of lightemitted from the emitter.
 55. The apparatus of claim 54 wherein theprobe assembly further includes a light tube disposed between the sightglass and the emitter.
 56. The apparatus of claim 54 wherein the sightglass is located along a side wall of the reaction vessel.
 57. Theapparatus of claim 54 wherein the vessel further includes mixingprovisions.
 58. An apparatus for polymerizing and/or crosslinking anadhesive or pre-adhesive composition, the apparatus comprising: areaction vessel defining an interior chamber, the vessel includingmixing provisions having at least one blade; at least one baffledisposed within the interior chamber of the reaction vessel, the baffleincluding at least one emitter for emitting light that polymerizesand/or crosslinks the composition.
 59. The apparatus of claim 58 whereinthe baffle is a uni-directional light emission baffle having a singleface that emits light.
 60. The apparatus of claim 59 wherein the baffleis oriented within the interior chamber such that upon operation of themixing provisions, the at least one blade moves toward the single faceof the baffle that emits light.